Hi, FullCircle,
I have had a daughter in trouble, and part of the trouble was abusing drugs and alcohol. I don't know if there is a way to know at an emotional level how to change your approach. I just had to do what was advised and deal with the fear and sadness that came as I did those things.
One thing that helped me through the process was that I knew for certain that what I had been doing hadn't helped anything or anyone- not me, her or my other daughter.
Is your child still a minor?